Electrical resistance type thermometer



Oct. 17, 1961 P. BECKMAN ELECTRICAL RESISTANCE TYPE THERMOMETER FiledAug. 19, 1960 FIG. 2

INVENTOR. Faa/ Beck/rm if ATTORN Y 3,005,171 ELECTRICAL RESISTANCE TYPETHERMOMETER Paul Beckman, Glen Olden, Pa. (944 Henrietta Ave, HuntingtonValley, Pa.) Fiied Aug. 19, B60, Ser. No. 59,633 2 Claims. (Cl. 338-28)This invention relates generally to resistance type thermometers andmore particularly to a thermometer of micro-miniature size.

It is an object of my invention to provide an improved electricalresistance thermometer whose principles of construction are such that itcan be effectively made in a simple and rugged mannepi i micro-miniaturesize, and, notwithstanding such minute size, will nevertheless record abroad range of temperatures.

It is another object of my invention to provide an improved electricalresistance type thermometer of extremely small size that will accuratelyproduce an electrical resistance change in response to temperaturecompletely independent of strain.

Other objects and advantages will be more apparent to those skilled inthe art from the following description of the accompanying drawings inwhich:

FIG. 1 is a greatly enlarged elevational view of my improved resistancethermometer;

FIG. 2 is a longitudinal sectional view of FIG. 1;

FIG. 3 is a cross-sectional view taken on the line 3-3 of PEG. 2; and

FIG. 4 illustrates an application, among many possible others, in whichmy thermometer is inserted in a turbine blade.

As shown in the drawings my invention consists of an elongated body orbulb 1 preferably circular in crosssection and made of high temperatureelectrical insulation material such, for example, as alpha alumina orberyllia oxide. This bulb is preferably about .033 in diameter and .500"long although both of these dimensions may be smaller. The bulb isprovided with two holes 2 and 3 extending lengthwise thereofsubstantially parallel to the bulb axis. A temperature sensitiveelectrical resistance element 4 of any usual and well-known material,whose electrical resistance varies with temperature through an adequatetemperature range, extends through these holes in a loop formation andhas its two ends suitably secured to connections 5 and 6. The reversingend of the filament is sealed by a suitable insulating cap 7 while thelead ends are similarly sealed by an insulating cap 8. Leads 9 of anysuitable length extend from the thermometer. The bulb material 1, ispreferably beryllia because of its very high thermal conductivityapproximating metal aluminum and the temperature sensitive resistanceelement 4 is preferably .0002 to .001 in diameter, thus showing theextremely minute nature of the electrical element and the miniature sizeof the bulb itself. The leads 9 are preferably comprised of nickel orplatinum tubing normally .007 CD. or smaller and are cold swaged to theelectrical resistance element 4.

p The leads are preferably anchored to the resistance bulb by mechanicalfriction inside the holes after which United States Patent 0" 3,005,171Patented Oct. 17, 1961 the resistivity of pure alpha alumina or berylliaoxidaplus,

the electrical insulating chacateristics oi air space between the wiresand the inside walls of each hole in the bulb, it having been noted thatthe resistance filament is loosely disposed within the holes 2 and 3thereby constituting an unbonded filament.

The use of an unbonded loosely disposed filament eliminates errors thatare generally introduced into conventional resistance thermometrywherein the standard methods of Winding resistance wires over insulatedmandrels introduces a strain error on temperature readout because of thehigh strain gage factor of these materials being tightly wound on themandrel. Consequently such wires feel the thermal coeflicient ofexpansionof the mandrel plus the resistance change due to stressrelieving of the wire under tension.

Thus it is seen that my invention provides a construction that not onlyallows the thermometer to be made in extremely small sizes in the formof a bulb but also eliminates the introduction of errors by thermaleffects or a change in resistance due to thermal expansion of thestructure for supporting the filament.

It will, of course, be understood that various changes in details ofconstruction and arrangement of parts may be made by thoseskilled in theart without departing from the spirit of the invention as set forth inthe appended claims.

I claim:

1. An electrical resistance type thermometer having an elongated bulb ofinsulating material provided with a pair of substantially parallel holesextending continuously throughout the length of the bulb, a lead at oneend of one of said holes and another lead at the corresponding end oftheother of said holes, and a temperature sensitive element ofelectrical conducting material extending through one of said holes inspaced relation to the wall thereof and reversely crossing over the endof the bulb and back through the other of said holes in spaced relationto the wall thereof, the ends of the filament being connected to theleads at one end of the bulb. I

2. The combination set forth in claim 1 further characterized in that aninsulation cap of ceramic material'embeds the cross-over portion of thefilament and seals the ends of the passages adjacent to said cross-overthereby to anchor the cross-over portion of the filament.

References Cited in the file of this patent UNITED STATES PATENTS UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N09 3 OO5 l7lOctober 17; 1961 Paul Beekman It is hereby certified that err entrequiring correction and that th corrected below.

or appears in the above numbered pate said Letters Patent should read asIn the grant lines 1 to 5 for "Paul Heekman of Glen Olden Pennsylvaniaread Paul Beekman of Huntington Valley Pennsylvania line l2 for PaulHeckman his heirs" read Paul Beckma n his heirs in the heading to theprinted specificstion lines 4 and S for "Paul Beckman Glen Olden Pa.(944 Henrietta Aveo V Huntington Valley Pao) read Paul Beckman 944Henrietta Aves 9 Huntington Valley Pa,

Signed and sealed this 17th day of April 1962;,

( SEAL) Attest:

ESTON e, JOHNSON DAVID L. LADD Attesting Officer Commissioner of PatentsUNITED STATES PATENT OFFICE CERTIFICATE F l Patent No S OOS 171 October17 1961 Paul Beckman It is hereby certified that error appears in theabove numbered patent requiring correction and that the said LettersPatent should read as corrected below.

In the grant lines 1 to 3 for "Paul Heekman of Glen Olden Pennsylvaniaread Paul Beckman of Huntington Valley Pennsylvania line 1.2 for "PaulHeckmen his heirs read Paul Beekmam his heirs in the heading to theprinted epecificatjion lines 4 and 5 for Paul Beckman Glen Olden Pa (944Henrietta Ave, 9 Huntington Valley Pas) read Paul Beckman 944 HenriettaAvee V Huntington. Willey Pan Signed and sealed this 17th day of April1962;

(SEAL) Attest:

ESTON e, JOHNSON DAVID L. LADD Attesting Officer Commissioner of Patents

